Optical receiver

In pattern synchronization for correctly regenerating received data, which is performed in an optical receiver for receiving an optical signal that has been subjected to quadrature phase modulation, signal conduction is quickly established without using duplicate combinations of bit shifting and pattern changing. A control method that does not involve verifying the duplicate combinations generated in modulation formats and pattern synchronization search orders. Specifically, a signal check circuit (40) performs data verification of data multiplexed by a MUX circuit (38) for multiplexing two data strings, and a bit shift pattern change control circuit (41) controls a bit shift circuit (36) and a pattern changing circuit (37) based on a result of the data verification and detects a correct combination of correct regenerated data to establish the signal conduction. At this time, for the bit shift circuit (36) and the pattern changing circuit (37), the duplicate combinations are not verified.